General patterns in the bottom communities in the seascapes

Length frequencies of spotted hake collected in beam trawl surveys of the New York & New Jersey seascapes in 2008 & 2009.  Fish less than 1 year in age (age-0) were represented by individuals less than 70 millimeters in length.  These age-0 fish were only collected in New Jersey.

Shell height frequencies for sea scallops collected in beam trawls towed in the New York & New Jersey seascapes in 2008 & 2009.  At least 2 height/age classes of scallops were represented in our collections and scallops were consistently more abundant off New York.


Fancy statistics are useful but if a data summary and simple graphs don't reveal a few intriguing trends, no amount of statistical hokus pocus will make the data interesting.  So in an effort not to lose the forest for the trees below is a general summary table that I admit is a little difficult to read (The fancy statistics will come later). The table lists the percent occurrence and mean abundance of species we collected in 2 meter beam trawls in the two seascapes during 2008 and 2009 using the methods described earlier. 


Species richness and patterns of age & size
Over the two years we collected 34 fish species and 19 invertebrates. Based on the animals lengths, 5 fish and 3 invertebrates were represented by more than one age class including an early juveniles less than a year old. Animals less than 1 year old are labeled age 0 in the table. For example age 0 spotted hake were represented in our trawl collections by fish less than 70 millimeters (mm) long. We collected at least two age classes of sea scallops; the youngest less than 40 mm in shell height. In addition northern sea robin, four spot flounder, black sea bass, windowpane flounder as well as rock crabs and long fin inshore squid used habitats in at least one of the seascapes as early juvenile nurseries.


The dominant fish species we collected were little skate, age 1+ spotted hake, butterfish, smallmouth flounder and gulf stream flounder. These last two species were among the 7 flatfishes occurring in our trawl samples. The butterfish we collected were all young juveniles. The most common invertebrates were seven-spine bay shrimp, sea stars, age 0 rock crabs, sand dollars, and spider crabs.


General differences between Seascapes
 Fish



A number of fish species appeared to be more common in the New Jersey seascape.  These included little skate, age 1+ spotted hake, bay anchovy were more common in New Jersey than New York while age-0 spotted hake collected exclusively in New Jersey over the two years. This suggests that larval delivery mechanisms and/or survival rates of newly settled spotted hake might make the New Jersey habitats more suitable nurseries. Butterfish and sand lance were also more abundant in New Jersey. Sand lance were rare in beam trawls, but these skinny little fish that live in sandy burrows were commonly captured on our underwater video and were dominant prey of the skates we collected in New Jersey during the early summer survey of 2008. The predators are always better samplers than we are. Gulfstream flounder, Red hake, age-0 searobin and striped searobin were more abundant in 2009. During that year the gulfstream flounder and red hake were more common in New York.


Invertebrates

Among invertebrates sevenspine bay shrimp and spider crabs were more common in the New York seascape. Age-0 rock crabs, which were very important prey for many of the animals we collected, were also slightly more common in New York. Sand dollars were more abundant in New Jersey in 2008 while age-0 longfin inshore squid were more abundant in that seascape in 2009.


Sea stars were consistently more abundant in our New Jersey collections. These animals are important predators of young sea scallops.   In the plot above of scallop shell heights, the smallest year class in 2008 is visible as a strong second size mode in 2009.  All year classes of sea scallops were more abundant in New York than New Jersey.  This might indicate that the settlement and survival of this 2008 cohort was high in New York. Differences in encounter rates of sea star predators with sea scallop prey in the two seascapes may be partially responsible for the differences in scallop abundance we observe.  This is just the kind of hypothesis we can test in field experiments to identify the seascape characteristics that effect the dispersal, growth and survival of animals that use the areas as nurseries. (Thanks to Jessica Lajoie for helping to get this information together)

A brief pelagic interlude

Densities measured with CTDs along the 4 transects on which we 

collected depth stratified plankton samples with a tucker trawl from 

August 9-12, 2010.   

I am trying hard to focus on the analysis of differences in fish and invertebrate bottom communities in the seascapes to follow up the last post about our bottom sampling methods.  But sometimes fun stuff happens.  First, Chip Haldeman from RUCOOL plotted up the density data we collected with CTDs during our plankton cruises last week. His waterfall plots are just too cool not to share.  Notice the highest density water (darkest red; cold & salty) in the head of the Hudson Shelf Valley in deep water off New Jersey.  The Steven's institute NYHOPs model showed a slug of cold salty water off the mouth of the estuary which could have welled up along the shelf valley. We had strong upwelling conditions all of last week. We tried to sample the plankton in the cold water on August 11th along the New York transect oriented southwest to northeast in the plot above. The positions of our tucker trawl tows on the NYHOPs model temperatures on the 11th are shown immediately below.

 Positions of the tucker trawls on NYHOPs forecast 

temperatures on August 11, 2010 showing the cool water
off the mouth of the estuary. This transect is also shown
stretching southwest to northeast in the plot above. 

RUCOOL used our CTD data to decide how to ballast a robot glider launched today off Sandy Hook.  The glider is to fly from Sandy Hook south to Cape May, New Jersey in a zigzag pattern from the near shore to 40 km offshore.  The glider will provide Steven's institute with temperature and salinity data to better tune the NYHOPs model for near shore forecasting.  It is also equipped with a dissolved oxygen and other optical sensors that will be used in the State of New Jersey's water quality monitoring program. This is exactly the kind of model tuning and habitat condition data we need to do our seascape work better.

At the last minute RUCOOL asked us if we could help with a vessel to launch the glider.  This was invitation for real fun.  Below are some pictures of the robot glider launch and a pod of porpoises that we saw on the way home. The mission of glider RU-16 over the next few weeks can be followed here.

Location where we launched the RU-16 glider on 8/20/2010 overlaid upon the surface salinity forecast from the NYHOPs model.  NYHOPs indicated that we launched the robot on the estuarine plume front which is why we may have had some buoyancy issues with the glider.

Launching the "bird" from the Research Vessel "The Torch".  Highlands New Jersey is in the back round on the right.

The "bird" at the surface.  The glider has a satellite telephone in its tail so the COOL room can upload instructions and download data to the robot anywhere in the world.

The pod of porpoises we saw on the way home about 1/2 mile off Sandy Hook.

Methods of sampling the bottom communities in the Seascapes

Egg capsules of longfin inshore squid captured on videotape

of the seabed in the New York seascape using the camera 

sled described below.   

Many of the larval fish, crabs and molluscs we collect in our tucker trawl on plankton cruises are probably just passing though the seascapes off Rockaway, New York and Seabright, New Jersey like all the ships traveling inbound and outbound from New York Harbor.  However some may settle out of the plankton to become small juveniles that use the seascapes and adjacent areas as nursery grounds.  Th­e New York Seascape is often supplied with water flowing from the east along the south shore of Long Island and Block Island Sound, while the New Jersey seascape usually receives surface water flowing out of the Hudson-Raritan river estuary, as well as deeper offshore water flowing inshore when winds from the south drive coastal upwelling.  Since the sources of water to the seascapes are often so different, the communities of animals occupying bottom habitats could reflect differences in larvae in the water masses.  If the bottom communities are different there are other plausible explanations too.  For example larvae settling as juveniles could suffer much higher predation mortality in one of the seascapes, while some older animals could be residents in one seascape rather than the other because oceanographic barriers restrict their movements.  Answering these questions requires that we measure differences in the rates animals are eaten by predators or the pathways over which they move in the ocean. These processes are very difficult to measure in the sea. Like all things ecological these and perhaps other processes are probably going on simultaneously to greater or lesser degrees.  In our study we chose to answer the easiest question first. Are there differences in the juvenile and adult communities in the seascapes that are related to the supply of baby fish and crabs to them? Knowing the answers to this questions should allow us to ask the more difficult ones more specifically and with more nuance in the future.

New Jersey and New York seascapes.  Dark brown patches are
fine sand and mud, light brown patches are sandy based on
classified side scan sonar imagery.  Depth  contours are shown
in the closeup image of the New Jersey seascape.  Blank areas
in the seascapes are located where the rocky reef and other hard
structures prevented us from towing the video sled and two
meter beam trawl on the bottom.

Are there differences in the bottom communities of fish and invertebrates in the two seascapes?  We performed trawl and underwater video surveys of bottom habitats in 2008 and 2009 to answer that question.  We were careful to choose seascapes with similar bottom types on either side of the mouth of the Hudson Raritan river estuary.  Choosing similar bottom habitats allowed us to estimate the relative contributions of fine scale variation in the seabed characteristics as well as broader scale circulation patterns to making animal communities different between and within the seascapes. We used maps of bottom depth and sediment type based on sidescan sonar to divide up the bottom so that each seascapes had equal proportions of fine sand and mud, medium sand and hard bottom habitat patches in both  “shallow” and “deep” areas (Lathrop et al. 2006).   The surface area of the seabed in each of the seascapes was ~ 95 km^2 (~37 miles ^2).   Shallow areas ranged in depth from 10 to 20 meters. The deep areas ranged from 20 to 30 meters (~100 feet) which was as deep as we could sample using the boat and gear available to us.  Within the deep and shallow areas, fine and medium sand and hard bottom habitats made up about 1/3 of the surface area of the bottom.

The video camera sled with a low light Deep Sea power
and light camera (the black thing in the center) and a
conductivity temperature and depth probe mounted at the
top of the frame. The length of chain at the bottom of the sled
is a "tickler" that flushes the critters out into the field of view
of the video camera. (see the videos at the end of the post).

The two meter beam trawl which we towed immediately adjacent
to the track of the video sled to capture live animals for verifying
video imagery and to characterize the food webs in the seascapes

We towed a video camera sled and a 2 meter beam trawl to sample fish, invertebrates and bottom habitats in the seascapes.  We limited our sampling to the patches of fine and medium sand because we could not tow our gear over more complex hard bottom. We conducted the surveys during the late Spring (Late June), Mid Summer (Late July through early August) and the Autumn (late September through early October) to identify the seasonal changes in the habitat associations of fish and invertebrates. During each survey we randomly selected two patches in the two types of soft bottom habitat (fine and medium sand) in each depth zone (shallow and deep) within the seascapes (New York and New Jersey).  We randomly selected 2 sites within each "habitat patch" for towing the gears. Thus we sampled animals and their habitats at 32 locations in each survey (2 sites x 2 patches x 2 sediment types x 2 depth zones x 2 seascapes x 3 seasons x 2 years = 192 sites total).  After measuring the vertical structure of the water column at each site with a conductivity, temperature and depth profiler (CTD) we towed the video sled at speed of about 1 knot (0.51 meters per second) for 10 minutes over ~ 300 meters of bottom. Our sled which was designed after Spencer et al (2005) and equipped with a Deep Sea Power and Light low light video camera, allowed us to identify associations of fish and invertebrates with fine scale characteristics of the seabed, including sizes and wavelengths of sand waves and the presence and absence of burrows and pits made by animals (see video below).  We also attached a CTD probe that measured temperature, salinity, oxygen and PH to the sled, and used our ADCP to measure current speeds over the bottom during every second of tow. These instrument allowed us to relate the presence and absence of animals on video to changes in the characteristics of overlying bottom water as well as to the structure of the seabed itself.  After hauling back the video sled we immediately towed a two meter wide beam trawl (with a 3 mm mesh net) parallel to, but 10 to 20 meters to one side of, the sled track. We counted and measured all of the animals collected in these trawls.  The live animal samples allow us to confirm the identities and sizes of the animals we collected in the video sled images.  They also allowed us to perform dietary analysis to see whether the food webs in the seascapes were different. In the next few posts we will try to summarize some analyses of differences in the juvenile and adult bottom communities.

The video immediately below of the sea scallop swimming was collected in the deep portion of the New York Seascape, while the videos of lobster (middle video) and windowpane flounder (bottom video) were collected in the New Jersey Seascape.  There were many lobster burrows in the dredge spoils from the deepening of the port of New York that were deposited in the north east corner of the New Jersey seascape.  At the start of the middle video of the lobster the sled also passes over a large rock crab sitting in a burrow.

Spencer, M. L., A. W. Stoner, C. H. Ryer, and J. E. Munk. 2005. A towed camera sled for estimating abundance of juvenile flatfishes and habitat characteristics: Comparison with beam trawls and divers. Estuarine, Coastal and Shelf Science 64:497.

Lathrop, R. G., M. Cole, N. Senyk, and B. Butman. 2006. Seafloor habitat mapping of the New York Bight incorporating sidescan sonar data. Estuarine, Coastal and Shelf Science 68:221.

Tucker trawl and plankton catch, August 10, 2010

Recent sea surface temperatures from satellites

Looks like upwelling along NJ and LI coasts after some recent days of westerly and earlier southerly winds. Come aboard for our August ECOS cruise starting tomorrow, Monday August 9.

Sampling off Long Island on the last day of our June cruise

A fine looking fishing vessel off the Rockaways, Long Island

Yesterday we completed the last day of our 4 day June sampling cruise. Earlier I remarked about how lucky we were to have winds shift from the south to north after we sampled each of the seascapes once. The plot on the left shows the northward and eastward components of the wind over the last few days at the “Ambrose” buoy off the mouth of the Hudson-Raritan Estuary. Our sampling periods are indicated by the hatched bars. Winds blew toward the east throughout the 4 cruises but shifted from the south to the north midway through the week. (The plots indicate the direction the wind is pushing water towards rather than the direction the wind is blowing from.  This is a convention of the physicists and all fish biologists suffer physics envy.  But why is ocean physics really interesting?  Because it matters to the fish.)

The effects of the wind shift on the oceans surface is evident in the 24 average surface currents measured with HF radar at 1300 each of the days we sampled (You can animate hourly 24 hour averaged surface currents at the RU COOL HF radar site). In these images you can see the wind drive strong offshore flow particularly along the southern flank of the Hudson Shelf valley early in the week. This flow weakened dramatically as the winds shifted southward. As a result of this change in winds the warm water we sampled relatively close to the coast of Long Island on Tuesday had moved well offshore into the mid-Atlantic bight on Thursday (7/30/10).   

The edge of the warm water is indicated by arrow in this 1030 GMT  satellite image of sea surface temperature.  On clear mornings we can count on getting one good early morning satellite image.  Once the land heats up and clouds form the images are not so useful.

This google earth map shows the NYHOPs model prediction of temperature and surface current flows for 1400 GMT which was about the time we began to sample. The beginning and ends of our transect as well the site of the front we selected from the NYHOPs model (mid_07012010) and the site of the  front from the satellite image above are marked. We towed our plankton net at 6 stations instead of usual 5 along this transect so we could sample locations of the front indicated by both the model and the satellite image.   

The acoustic image of particle backscatter along our transect to the left is from our acoustic doppler current profiler.  The rectangles show the 6 locations where we towed the plankton nets.  TT_3_1506 is the site of front in the NYHOPs model and TT_4_1558 the site of the front in the satellite image above with the arrow.  The 4 digit numbers at the end of the station designations are the Greenwich mean times (GMT) of the sampling. We use GMT time so that it is easy to match our data with data collected by satellites and other sensors available through the ocean observing system.

The image below shows in much more detail the scattering layers we towed our net through at station 2 (TT_2_1430).  We fished one net from the surface to a depth of 9 meters, and a second net from 9-23 meters.  We selected these depths based on this image and the CTD cast (not shown. But see earlier post).  There seems to be a lot going on down there.  In general the acoustic complexity of the water column on the transect to Long Island on thursday was greater than on the other 3 days of the week.  This CTD data also seemed show this but we haven't processed the data yet. We have a lot more data to processes including the plankton samples which we now need to sort.

  

Who makes ECOS possible?

Today was the last day of our June ECOS cruise.  We had another of interesting day sampling on a long transect perpendicular to Long Island, New York.  Our last sample was collected in cold salty water more typical of New England and we captured some larval fish at several stations.  The day deserves description, from it's interesting oceanography to the fin whale we saw rolling toward the north off the tip of Sandy Hook. It rolled into brown water of the Hudson-Raritan river plume that ran between the bank of sand that is the New Jersey coast and the invisible riverbank on its eastern flank made by the north wind and the salty water of the Atlantic ocean.  But I'm too tired right now to process the data required to do the day real justice.

But I want to express my gratitude to Jeff Pessutti.  During all 4 days of sampling the complex integrated equipment and operations worked as smoothly as silk.  That was only possible because of the ingenuity, effort and careful work of Jeff who can take every crazy idea I can think of and make it happen using nothing but bailing wire, duct tape, and a few pieces of equipment, some of it begged for, borrowed, or ...... The ECOS research project could not happen without him. I can say the same about every other research project I've successfully completed over the past 10 years, but this project is technically the most sophisticated.

The vertical structure of the ocean off New Jersey

Stations where we sampled with nets today (6/30/2010) and where the CTD casts and acoustic images of the ocean referenced below were collected.  For discussion of our route planning see the earlier post today.

We use satellite, HF radar, oceanographic models and a surface conductivity, temperature and depth (CTD) sensor (the bottom left window on the computer screen) to identify surface features and position our stations in relation to those features.  To determine depths at which to fish our nets at those stations we use instruments that use sound to measure and visualize ocean structure, along with a profiling CTD.  To the left is the computer monitor on the bridge of the ship that shows real time pictures of the ocean made with sound by  acoustic instruments.  On the top is the output from an acoustic doppler current (ADCP)  profiler that emits and measures the return of high frequency sound at 600 khz.  The panel on the top left shows a vertical cross section of current speed. The middle panel at the top shows current direction and the right panel is acoustic backscatter. On the bottom right is an image of the ocean made with a longer frequency fishery hydroacoustic instrument that emits and measures the return of sound at 120 khz.  The 600 khz machine, with its shorter wavelengths of sound, will "see" smaller critters in the ocean than the 120 khz machine.

This panel shows the acoustic backscatter from the ADCP measured across the entire early morning transect we used to verify the features in the model and remotely sensed data (The map of our track is in the last post).  Inshore at mid depth there is a region of low backscatter (purple).  Offshore there are areas of high scattering (pale blue & green)  at mid-depth and deep.  The ship and pole arm on which the acoustic transducers are mounted make a lot of turbulence as they move through the water. As a result it is impossible to distinguish sound scattered by the turbulence or by particles at the surface.

We also use the CTD profiler (to the left) to see the structure of the water beneath the oceans surface .  We have added seine floats to the instrument to make it nearly neutrally bouyant and sink very slowly. As a result it makes many more measurements over the distance it sinks.  This allows us to identify small changes in water density and other characteristics over at scales as small as a few centimeters. This kind of fine scale structure in the water column is often ignored. But a typical larval fish is neutrally bouyant and less than about 15 mm, or about a half an inch long.  Because of this slight changes in density and other characteristics over distances of ranging from a few centimeters to a few meters probably make up important components of the seascape to larval fish. The scales of habitat variation should match the body size and movement scales of the animals.  So maybe larval seascapes are the "Hunt for Red October" in miniature, filled with invisible hedge rows made of structured water the larvae can hide behind and graze near.

We combine visualizations of the acoustic and CTD data to decide how deep to tow the nets.  The 5 plots below overlay the CTD profiles on top of the acoustic images of the ocean made with fishery hydroacoustics right before we fish each net. In all the plots the colored lines represent the following water column characteristics: Red=salinity, dark blue=temperature, light blue=oxygen, green=Chlorophyll-A pigment of plants, and black=turbidity, or tiny particles in the water column.



After taking this CTD cast and looking at the acoustics at this station furthest offshore we decided to fish a net from 0 to 7 meters to capture plankton at the surface.  We then used a second net to fish between 7 and 25 meters.  This is the best we can do with the equipment we have.  A 5 net electronic opening and closing net would much better but also would cost about $200k when we got through with the necessary wiring and electronics on the boat.  So the net we have will have to do for a while.  In the surface tow at this station we caught a baby seahorse and lobster.

Letting the tucker trawl out to fish.

The seahorse (closer to the quarter) and the lobster (farther from the quarter) we caught in the surface layer between 0 and 7 meters at our offshore station.  We should "look" at these organisms in our laboratory with the different frequencies of our acoustic instruments.  This might allow us to verify their acoustic signatures and one day identify lobster larvae and their locations in the water just by the return of the sound.

Acoustic image and CTD casts at station 2 (see previous post for map) Something big (the blue streak) was rising to the surface here (No it wasn't the CTD).

Acoustic image and CTD casts at station 3 (see previous post for map)

Acoustic image and CTD casts at station 2 (see previous post for map)

And below is the acoustic image and CTD casts at station 1 closest to the beach near Sandy Hook (see previous post for map).  Their often eem to be more scattering layers that coincide with steps in the density of the water along the shoreline near Sandy Hook because the flow of freshwater from the Hudson River plume pulses in with the tide. However the vertical structure of the water column in New Jersey seems to be relatively simple this year perhaps because it has been so dry (see earlier post).

A plan for the early morning transect off New Jersey

06/30/2010 11:46:42 GMT

Could we be any luckier? After a week or more of strong winds from the south and southwest that produced upwelling conditions along the New Jersey Coast, late yesterday afternoon the wind shifted north west and peaked at 20 knots at the Ambrose buoy.  On monday we sampled across the upwelling front off New Jersey. Because of the wind shift, today we will be sampling under downwelling conditions with the Hudson-Raritan estuarine plume streaming like a river along the New Jersey coast. The 1400 GMT NYHOPs model forecast of salinity and currents is plotted on the left. Our start and end points for the morning exploratory transect are indicated by the red symbols off the Coast. The white symbol is the approximate position of the eastern edge of the Hudson River Plume forecast by the NYHOPs model. We will run the exploratory transect quickly with our acoustic and surface CTD to confirm the position of the plume front in the model before we start fishing.  Somebody on board just sighted a whale to the north outside the mouth of the estuary where in the distance we can also see the Verizano bridge and Manhattan towers burning in sunlight and clawing their way higher into the sky.

A Cruise to New York (continued)

Once we arrived at the inshore point on the Google Earth map pictured in the 2nd to last post, we turned toward the southeast to try to slice into the warm fresher water we saw in the model and ocean observations. The map to the left shows a rapid morning transect and histograms of the density (sigma_theta), salinity, and temperatures we measured at the surface along the way. We don't fish on this first transect; just collect physical and acoustic data to pinpoint where our samples should be when we turn around and retrace our steps later in the day.  Early and inshore where the water was cold and salty, we saw Mother Carey's chickens (Wilsons Storm Petrel ) pattering the water, fishing for plankton with their feet. The clam dredge boat below was working about half way along the transect in an offshore anchorage where cargo ship wait to be permitted entry to New York Harbor.

When we finished this exploratory transect we quickly plotted up the data and found that it confirmed the model, satellite and HF radar observations of inshore to offshore gradient of cold salty water to warm fresher water.

A Mother Carey's Chicken
(Wilson's storm petrel)

The clam dredge











This is the track we took toward Long Island on return trip when we fished the tucker trawl.  It is colored by the density of the surface water with less dense warm and fresher offshore water in light blue and more dense cold and salty water inshore in red.  (A plot of surface water PH looks very similar but with low PH inshore; higher PH offshore). The green dots along our track indicate the 5 locations where we towed the tucker trawl for plankton. The red dots are the locations where we  did casts with our conductivity, temperature, depth profiler (CTD) to map out the vertical structure of the water column. (We also do CTD's at the plankton sampling stations.)  Below are cross sections of temperature, salinity and density along our track that we made with our  CTD cast data.  The sharpest change in temperature and density occurred at about kilometer 12 or 13 where we made our third net tow (The third green dot in the map above)

The cross sections show a two layered ocean more or less. 

But is it really? 

The two acoustic images below taken during our first trawl tow offshore and last tow inshore suggest the vertical structure can be more complex.

This image shows at least 3 scattering layers in the area of our first net tow offshore.  And this is a simple structure compared to what we sometimes see in the vacinity of the Hudson Raritan River plume in our New Jersey Seascape.

Our basic sampling strategy is to use the ocean observations and models to map out our sampling in the horizontal dimension across the ocean surface.  (This would be impossible without an exceptional operational ocean observatory in the region run by friends at Rutgers University (http://rucool.marine.rutgers.edu/) and their collaborators in MARCOOS (http://www.marcoos.us/)).  We then look at our shipboard data; individual CTD casts, the fisheries hydro-acoustic images, our acoustic doppler current profiler, and make decisions on the fly as to how to partition the water column and determine the depths at which we will fish our net for larval fish.

 

This acoustic image was taken during the final tucker trawl tow of the day at the sampling station nearest to the Long Island shoreline. We are in shallow water and there was a fairly big ocean swell toward the shore (Big long waves).  The waviness of the bottom is from the heave of our "ship" in the swell.  The structure of the water column visible in this acoustic image was less organized than the structure in deeper water because of the waves in shallow water make more turbulence.

My larvae are on their way to you! - - Urophycis regia

And a Cruise to New York

06/29/2010 11:46:04

We are on our way to sample off New York today. After the coin flip at the start of each 4 day cruise we alternate sampling the seascapes so that if conditions change dramatically due to a storm we are not left sampling one seascape in dramatically different oceanographic conditions.  If we do get a storm we want to be able to sample in both seascapes immediately afterwards so we can measure the seascape differences in the "supply side" ecology?  If we were truly sampling adaptively we would sample whenever the oceanography developed that we wanted to explore. Unfortunately the nature of ship time makes that difficult to do.

Today the wind is out of the west south west (250T) at 10 knots at the Ambrose Bouy. We have a number of good Satellite and HF radar images today and that observational data is similar to the NYHOPs model pictured above.  As a result we are using the surface temperature and current flow from NYHOPs to route todays cruise. The forecast shows cold salty water near the shoreline of Long Island, and warm salty water offshore on the surface.   Our plan is to do a rapid morning transect  using just the surface CTD and acoustic instruments from the nearshore into the warm water bulge offshore before we put the net in the water. (between the red pushpins) 

A Cruise to New Jersey

As this was the first day of our June cruise, our intern, Jessica flipped the coin and it came up "New Jersey".  So we sampled ichthyplankton off New Jersey today. Our high speed wireless internet reception on the boat was consistently good so we were able use the Stevens Institute NYHOPS model output in google earth to route our sampling.  In the past we have depended only on near real time satellite (map 1, just to the left)and HF radar observations of the ocean (mat 2 below). Those data are great but the observations are at least an hour behind and cannot tell us what the ocean looks like at present or an hour in the future on our research ship.   The observations give us a view from space of what just happened in the ocean 1 to 48 hours earlier.  The assimilation model gives us a birds eye view of a good mathematical guess tuned with the real observations, of what the ocean looks like right now and in the near future (map 3 below).  With the NYHOPs we were looking at nowcasts or short term forecasts that seemed remarkable accurate and could tell us where we aught to sample an hour or more from the present.


As forecast, we had upwelling favorable conditions along the coast of New Jersey.  The wind at the ambrose bouy at 8AM (1200 GMT) was out of the southwest ( ~ 210T) at 12 knots. The early morning satellite image showed cool water near the New Jersey coast (map 1) and daily averaged HF radar current data (map 2) showed water moving offshore as a result of the southwest wind.

In the NYHOPs model (map 3) the edges of the Hudson Raritan River Plume defined the frontal boundaries in the area we would sample. In the forecast it appeared that the offshore edge of the estuarine plume would move east so quickly with the wind and ebbing tide that we wouldn't be able to keep up with our ship while sampling.  So we decided to target the inshore edge of the estuarine plume and the area of upwelled water inshore.  

We laid out a transect from the nearshore to the edge of the Hudson Shelf Valley which we ran using just a YSI temperature, salinity and oxygen probe mounted on a pole arm at the surface along with fisheries hydroacoustics and an acoustic dopler profiler.  This rapid morning transect is the line between the two white symbols with black dots on this map of NYHOPs forecast surface salinities and current flows. The transect allowed us to identify where the strongest surface features were and confirmed the position of the inshore front in the NYHOPs model forecast.

The computer screen on the left shows the output of the fisheries hydroacoustics profiles (bottom panel), acoustic doppler current profile of surface current speed and direction (top panel).  On the upper right of the screen is data from the YSI CTD probe that is measuring salinity and temperature every second at the surface as the ship moves through the water.  This real time data helps us to identify structure in the ocean water we will sample.  Strong fronts and current shears are detected by these acoustic instruments as well as by sharp changes in temperature and salinities over short distances.  The acoustic instruments work by emitting sound and measuring its properties when it returns to ship after it has bounced off particles including animals.  As a result we can use the sound to tell us where the animals are beneath the surface of the ocean. 

Here is the salinity data we measured with the surface YSI during the morning transect to confirm the model.  We have overlaid it on a side scan sonar image of the bottom sediment. The western edge of the hudson shelf valley is on the right of the image.  The colored line is the salinity which is high (red) in a thin band along the coast coast and lower (light blue) offshore.  Surface temperatures were also as much as 5C lower inshore (20 C) than offshore.  This cold salty water along the coast was brought in from deep and offshore by the effects of the southwest wind driving the surface water offshore.  The green dots in the map are the locations where we did casts with a conductivity, depth, and temperature (CTD) profiler that also measures DO, Chlorophyll-A and turbidity.  The red dots are the locations where we towed the tucker trawl for larval fish.

To the left is our live ship track (red arrow) plotted in a Geographic Information System (GIS) along with the surface YSI data we measured in the morning.  The shapes are patches of different types of sediment on the bottom. We are able to import satellite ocean color and HF radar surface current data codar data into this GIS very quickly when we have a good internet connection.  But we didn't need to do that today because we were able to stay connected to the internet and with google earth at sea.  In the upper right part of the screen is the output from our last CTD cast of the day.

This is our tucker trawl for sampling larval fish at multiple depths.  We have strapped a YSI CTD with depth. temperature, salinity, oxygen, Chlorophyll-A, and turbidity sensors to the trawl and have a wire running from the net to the computers in the bridge of the ship.  We can therefor see exactly what depth the net is fishing as well as all the ocean characteristics at all times.  These data are also saved on the computer.  Using this system we can fly the net very precisely through layers we can see acoustic instruments and CTD casts.  In the end we have continuous records of the characteristics of the environment during in the water where the larval fish were caught.

A great naturalist (Linda Stehlik) who knows all the fish (and the birds) sieving a plankton sample which we will take home and sort in the lab.  Unfortunately the sorting takes months. There did not appear to be a lot of larval fish or crabs in our samples. (An update.  I was wrong. We have begun sorting and it turns out there is a lot more in these samples, including larval fish, than we could see on the ship with the naked eye.  More to come).

And finally this is the first of the data we collected today that we had time to process.  It is a cross section made from the temperature, salinity, and density CTD profile records collected along our inshore transect to sample planton with the net.  It shows that warm freshwater was on the surface offshore (down to about 4-5M) and a upwelling front was located at approximately km 9 of our track.  We sampled plankton with our tuckertrawl on this front as well as at two stations inshore and two stations offshore of it.  Based on the CTD casts, fisheries hydroacoustics and ADCP current profiles we decided to tow nets at the surface to a depth of 4 or 5 meters and then other nets from ~ 4 meters to a safe depth above the bottom at 4 of the 5 stations. The ADCP showed us that where the direction and speed with which the water was flowing. At the offshore stations it flowed in different directions at the surface, mid depth and bottom.  Fish larvae and other plankton at different depths may have been in different lanes of divided two and sometime three way highways.